Avoid discarding createEngines returned reference , or Down with art - - PowerPoint PPT Presentation

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Avoid discarding createEngines returned reference , or Down with art - - PowerPoint PPT Presentation

Sep 15, 2022 151 likes •327 views

Avoid discarding createEngines returned reference , or Down with art s getEngine! Kyle J. Knoepfel LArSoft Coordination Meeting 29 January 2019 Random number engines in art /LArSoft art provides random-number management via the

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SLIDE 1

Avoid discarding createEngine’s returned reference, or Down with art’s getEngine!

Kyle J. Knoepfel LArSoft Coordination Meeting 29 January 2019

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SLIDE 2

Random number engines in art/LArSoft

2

  • art provides random-number management via the RandomNumberGenerator

service.

– Engines are attributed to modules, using the createEngine(…) base-class member function.

  • To access the engine, just cache the returned reference from the createEngine call

CLHEP::HepRandomEngine& engine = createEngine(…);

  • Directly using the RandomNumberGenerator service has rarely been required.

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting

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SLIDE 3

Random number engines in art/LArSoft

3

  • art provides random-number management via the RandomNumberGenerator

service.

– Engines are attributed to modules, using the createEngine(…) base-class member function.

  • To access the engine, just cache the returned reference from the createEngine call

CLHEP::HepRandomEngine& engine = createEngine(…);

  • Directly using the RandomNumberGenerator service has rarely been required.
  • For nutools users, the NuRandomService has its own createEngine function:

– The NuRandomService::createEngine function wraps the art-provided function. – Until recently, the only way you could gain access to the engine was to call art’s RandomNumberGenerator::getEngine function.

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting

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SLIDE 4

Random number engines in art/LArSoft

4

  • art provides random-number management via the RandomNumberGenerator

service.

– Engines are attributed to modules, using the createEngine(…) base-class member function.

  • To access the engine, just cache the returned reference from the createEngine call

CLHEP::HepRandomEngine& engine = createEngine(…);

  • Directly using the RandomNumberGenerator service has rarely been required.
  • For nutools users, the NuRandomService has its own createEngine function:

– The NuRandomService::createEngine function wraps the art-provided function. – Until recently, the only way you could gain access to the engine was to call art’s RandomNumberGenerator::getEngine function.

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting

RNG::getEngine will be deprecated in art 3.02, removed in art 3.03

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SLIDE 5
  • It’s confusing.
  • Which engine does the following code use?

double random_number() { // Common to see in art 2 ServiceHandle<RNG> rng; auto& engine = rng->getEngine(); CLHEP::RandFlat rand{engine}; return rand.fire(); }

Problems with getEngine (art 2)

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 5

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SLIDE 6
  • It’s confusing
  • Which engine does the following code use?

double random_number() { // Common to see in art 3 ServiceHandle<RNG> rng; auto& engine = rng->getEngine(module_label, // Where do you get schedule_id); // these values? CLHEP::RandFlat rand{engine}; return rand.fire(); }

Problems with getEngine (art 3)

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 6

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SLIDE 7

Problems with getEngine

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 7

class MyProducer { public: MyProducer(ParameterSet const& pset) { ServiceHandle<NuRandomService>{}

  • >createEngine(...);

} void produce(art::Event& e) override { auto& engine = ServiceHandle<RandomNumberGenerator>{}

  • >getEngine(...);

CLHEP::RandFlat flatDist{engine}; flatDist.fire(...); } };

Common

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SLIDE 8

Problems with getEngine

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 8

class MyProducer { public: MyProducer(ParameterSet const& pset) { ServiceHandle<NuRandomService>{}

  • >createEngine(...);

} void produce(art::Event& e) override { auto& engine = ServiceHandle<RandomNumberGenerator>{}

  • >getEngine(...);

CLHEP::RandFlat flatDist{engine}; flatDist.fire(...); } };

Common

Expensive operations:

ServiceHandle created for each event getEngine called on each event RandFlat distribution created for each event

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SLIDE 9

What’s the better option?

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 9

class MyProducer { public: MyProducer(ParameterSet const& pset) { ServiceHandle<NuRandomService>{}

  • >createEngine(...);

} void produce(art::Event& e) override { auto& engine = ServiceHandle<RandomNumberGenerator>{}

  • >getEngine(...);

CLHEP::RandFlat flatDist{engine}; flatDist.fire(...); } }; class MyProducer { CLHEP::RandFlat flatDist_; public: MyProducer(ParameterSet const& pset) : flatDist_{ServiceHandle<NuRandomService>{}

  • >createEngine(...)}

{} void produce(art::Event& e) override { flatDist_.fire(...); } };

Common Better

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SLIDE 10

What’s the better option?

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 10

class MyProducer { public: MyProducer(ParameterSet const& pset) { ServiceHandle<NuRandomService>{}

  • >createEngine(...);

} void produce(art::Event& e) override { auto& engine = ServiceHandle<RandomNumberGenerator>{}

  • >getEngine(...);

CLHEP::RandFlat flatDist{engine}; flatDist.fire(...); } }; class MyProducer { CLHEP::RandFlat flatDist_; public: MyProducer(ParameterSet const& pset) : flatDist_{ServiceHandle<NuRandomService>{}

  • >createEngine(...)}

{} void produce(art::Event& e) override { flatDist_.fire(...); } };

Common Better

createEngine returns art-owned reference to engine; no need to directly interact with it

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SLIDE 11

What’s the better option?

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 11

class MyProducer { public: MyProducer(ParameterSet const& pset) { ServiceHandle<NuRandomService>{}

  • >createEngine(...);

} void produce(art::Event& e) override { auto& engine = ServiceHandle<RandomNumberGenerator>{}

  • >getEngine(...);

CLHEP::RandFlat flatDist{engine}; flatDist.fire(...); } }; class MyProducer { CLHEP::RandFlat flatDist_; public: MyProducer(ParameterSet const& pset) : flatDist_{ServiceHandle<NuRandomService>{}

  • >createEngine(...)}

{} void produce(art::Event& e) override { flatDist_.fire(...); } };

Common Better

You can do this now.

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SLIDE 12
  • I would like to make it a compile-time warning to discard the reference returned

when calling NuRandomService::createEngine.

To encourage better usage…

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 12

// The following statement is supported: engine_t& engine = ServiceHandle<NuRandomService>{}->createEngine(...); // The following statement generates a compile-time warning: ServiceHandle<NuRandomService>{}->createEngine(...);

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SLIDE 13
  • I would like to make it a compile-time warning to discard the reference returned

when calling NuRandomService::createEngine.

To encourage better usage…

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 13

// The following statement is supported: engine_t& engine = ServiceHandle<NuRandomService>{}->createEngine(...); // The following statement generates a compile-time warning: ServiceHandle<NuRandomService>{}->createEngine(...);

/home/knoepfel/scratch/larsoft-devel/srcs/larsim/larsim/EventGenerator/LightSource_module.cc:198:83: warning: ignoring return value of ‘std::reference_wrapper<CLHEP::HepRandomEngine> rndm::NuRandomService::createEngine(…) […]’, declared with attribute nodiscard [-Werror=unused-result] art::ServiceHandle<rndm::NuRandomService>{}->createEngine(*this, pset, "Seed2");

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SLIDE 14
  • I would like to make it a compile-time warning to discard the reference returned

when calling NuRandomService::createEngine.

  • In rare circumstances, the warning can be silenced by casting to void:

To encourage better usage…

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 14

// The following statement is supported: engine_t& engine = ServiceHandle<NuRandomService>{}->createEngine(...); // The following statement generates a compile-time warning: ServiceHandle<NuRandomService>{}->createEngine(...);

/home/knoepfel/scratch/larsoft-devel/srcs/larsim/larsim/EventGenerator/LightSource_module.cc:198:83: warning: ignoring return value of ‘std::reference_wrapper<CLHEP::HepRandomEngine> rndm::NuRandomService::createEngine(…) […]’, declared with attribute nodiscard [-Werror=unused-result] art::ServiceHandle<rndm::NuRandomService>{}->createEngine(*this, pset, "Seed2");

(void)ServiceHandle<NuRandomService>{}->createEngine(...);

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SLIDE 15
  • I would like to make it a compile-time warning to discard the reference returned

when calling NuRandomService::createEngine.

  • In rare circumstances, the warning can be silenced by casting to void:

To encourage better usage…

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 15

// The following statement is supported: engine_t& engine = ServiceHandle<NuRandomService>{}->createEngine(...); // The following statement generates a compile-time warning: ServiceHandle<NuRandomService>{}->createEngine(...);

/home/knoepfel/scratch/larsoft-devel/srcs/larsim/larsim/EventGenerator/LightSource_module.cc:198:83: warning: ignoring return value of ‘std::reference_wrapper<CLHEP::HepRandomEngine> rndm::NuRandomService::createEngine(…) […]’, declared with attribute nodiscard [-Werror=unused-result] art::ServiceHandle<rndm::NuRandomService>{}->createEngine(*this, pset, "Seed2");

(void)ServiceHandle<NuRandomService>{}->createEngine(...);

Making this change now will position LArSoft for art 3.02, when getEngine is deprecated by art.

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SLIDE 16
  • Make it a compile-time warning to discard the reference returned when calling

NuRandomService::createEngine.

  • Under-the-covers technical change:
  • Feature branches available:

– nutools:feature/knoepfel_nodiscard – larsim:feature/knoepfel_nodiscard – larreco:feature/knoepfel_nodiscard – larana:feature/knoepfel_nodiscard

  • Will provide feature branches for experiments if the above change is accepted.

The proposal

1/29/19 Kyle J. Knoepfel | LArSoft coordination meeting 16

  • engine_t& createEngine(...)

+ [[nodiscard]] std::reference_wrapper<engine_t> createEngine(...)